Mixed mode digital control for switching regulator

ABSTRACT

A regulated power supply includes an inverter comprising an upper switch and a lower switch that are connected in series. A control module selectively controls the upper switch and the lower switch in one of a pulse width modulation (PWM) mode and a discrete control mode (DCM), receives a feedback signal from an output of the regulated power supply, and switches between the PWM mode and the DCM based on the feedback signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 11/227,387, filed Sep. 15, 2005, which claims thebenefit of U.S. Provisional Patent Application No. 60/675,791, filedApr. 27, 2005. The disclosures of the above applications areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to voltage regulators, and moreparticularly to control systems for voltage regulators.

BACKGROUND OF THE INVENTION

A voltage regulator converts an unregulated input voltage to a regulatedoutput voltage. A voltage set point determines a magnitude of theregulated output voltage. The voltage regulator includes a controlmodule that compares the voltage set point and the regulated outputvoltage and adjusts the regulated output voltage in accordance with thecomparison.

The control module typically includes an analog-to-digital converter(ADC) having an input that receives the regulated output voltage. TheADC converts the regulated output voltage, which is an analog signal, toa digital value that can be used by the control module. The ADC has aninput voltage range and an output resolution that are both generallyfixed. For example, a particular ADC may be a 3-comparator design thathas an input voltage range of V*+/−δ, where V* is the voltage set pointand δ is a maximum output swing of the ADC. This example ADC could thenprovide a binary count of 00 when the regulated output voltage is belowV*−δ, a binary count of 01 when the regulated output voltage is betweenV*−δ and V*, a binary count of 10 when the regulated output voltage isbetween V* and V*+δ, and a binary count of 11 when the regulated outputvoltage is greater than V*+δ.

Referring now to FIG. 1, the regulated output voltage 10 is shownrelative to the voltage set point V*. The lower limit of the ADC inputvoltage range is at V*−δ. The upper limit of the ADC input voltage rangeis at V*+δ. The voltages are measured with respect to a referencepotential, such as ground, that is represented by a reference line 12.

The regulated output voltage 10 should remain between V*−δ and V*+δ forthe ADC to generate the binary count that represents the actualmagnitude of the regulated output voltage 10. When the regulated outputvoltage 10 goes above V*+δ or below V*−δ, it is “out of range”. When theregulated output voltage 10 goes out of range, such as is shown at peaks14-1, 14-2, . . . , 14-5, referred to collectively as the peaks 14, theADC is unable to provide a binary count that represents the actualmagnitude of the regulated output voltage 10. Therefore, during thefirst peak 14-1, the control module is unable to determine a magnitudeof difference between the voltage set point V* and the regulated outputvoltage 10. The remaining peaks 14-2, . . . , 14-5 show that the controlmodule has become unstable due to the first peak 14-1.

One way to prevent the voltage regulator from becoming unstable when theADC goes out of range is to use an ADC that has a larger input voltagerange. However, increasing the input voltage range generally alsorequires increasing the ADC output resolution, which causes the ADC toincrease in size, cost, and power consumption.

SUMMARY OF THE INVENTION

A regulated power supply is provided that includes an invertercomprising an upper switch and a lower switch that are connected inseries. A control module selectively controls the upper switch and thelower switch in one of a pulse width modulation (PWM) mode and adiscrete control mode (DCM), receives a feedback signal from an outputof the regulated power supply, and switches between the PWM mode and theDCM based on the feedback signal.

In other features, the regulated power supply includes an analog todigital converter (ADC) that receives the feedback signal and thatgenerates an ADC count. The control module receives the ADC count andswitches between the PWM mode and the DCM based on the ADC count. Thecontrol module compares the feedback signal to a range and switchesbetween the PWM mode and the DCM when the feedback signal is outside ofthe range.

In other features, the regulated power supply includes a current sensorthat senses current and generates a current signal. The DCM includes atransient DCM and a steady-state DCM, and the control module switchesbetween the transient DCM and the steady-state DCM based on the currentsignal.

In other features, the regulated power supply includes an energy storagedevice connected to the inverter. The control module charges the energystorage device by placing the inverter in an up state until a currentthrough the energy storage device reaches a first predetermined currentand the duration of the up state is T_(up). The control moduledischarges the energy storage device by placing the inverter in a downstate until the current through the energy storage device reaches asecond predetermined current and the duration of the down state isT_(down). The control module tracks a time T_(off) that is based on anoutput voltage of the power supply reaching a predetermined voltage. Thecontrol module switches from the DCM to the PWM mode after a timeT_(load) that is based on the times T_(up), T_(down), and T_(off). Acapacitor has one end connected to the energy storage device and theenergy storage device includes an inductor.

A method for operating a regulated power supply is provided and includesreceiving a feedback signal from an output of the regulated power supplyand selectively using one of a pulse width modulation (PWM) mode and adiscrete control mode (DCM) to generate an output voltage. The selectionis based on the feedback signal.

In other features, the receiving step includes generating ananalog-to-digital converter (ADC) count based on the feedback signal.The selectively using step selects between the PWM mode and the DCMbased on the ADC count. The method can also include comparing thefeedback signal to a range, and selecting between the PWM mode and theDCM based on the feedback signal. The DCM includes a transient DCM and asteady-state DCM and the method includes reading a current signal andselectively, based on the current signal, using one of the transient DCMand the steady-state DCM.

In other features, the method can include providing an energy storagedevice within the regulated power supply. The method includes chargingthe energy storage device until a current through the energy storagedevice reaches a first predetermined current and wherein the duration ofthe charging is T_(up), discharging the energy storage device until thecurrent through the energy storage device reaches a second predeterminedcurrent and wherein the duration of the discharging is T_(down),tracking a time T_(off) that is based on the output voltage reaching apredetermined voltage, and switching from the DCM to the PWM mode aftera time T_(load) that is based on the times T_(up), T_(down), andT_(off). The method can include connecting one end of a capacitor to theenergy storage device, and the energy storage device can include aninductor.

A regulated power supply is provided that includes inverter meanscomprising upper switch means for switching and lower switch means forswitching that are connected in series. The regulated power supply alsoincludes control means for selectively controlling the upper switchmeans and the lower switch means in one of a pulse width modulation(PWM) mode and a discrete control mode (DCM), that receives a feedbacksignal from an output of the regulated power supply and that switchesbetween the PWM mode and the DCM based on the feedback signal.

In other features, the regulated power supply includes analog to digitalconverter (ADC) means for receiving the feedback signal and generatingan ADC count. The control means receives the ADC count and switchesbetween the PWM mode and the DCM based on the ADC count. The controlmeans compares the feedback signal to a range and switches between thePWM mode and the DCM when the feedback signal is outside of the range.

In other features, the regulated power supply includes current sensormeans for sensing current and generating a current signal, wherein theDCM includes a transient DCM and a steady-state DCM, and wherein thecontrol means switches between the transient DCM and the steady-stateDCM based on the current signal.

In other features, the regulated power supply includes storage meansconnected to the inverter means. The control means charges the energystorage means by placing the inverter means in an up state until acurrent through the energy storage means reaches a first predeterminedcurrent and wherein the duration of the up state is T_(up). The controlmeans discharges the energy storage means by placing the inverter meansin a down state until the current through the energy storage meansreaches a second predetermined current and wherein the duration of thedown state is T_(down). The control means tracks a time T_(off) that isbased on an output voltage of the power supply reaching a predeterminedvoltage, and the control means switches from the DCM to the PWM modeafter a time T_(load) that is based on the times T_(up), T_(down), andT_(off).

In other features, the regulated power supply includes capacitor meansfor providing a capacitance that is connected to the energy storagemeans. The energy storage means includes inductor means for providing aninductance.

A regulated power supply is provided that includes an invertercomprising an upper switch and a lower switch that are connected inseries. A control module selectively controls the upper switch and thelower switch in one of a pulse width modulation (PWM) mode, a transientdiscrete control mode (DCM), and a steady state DCM and receives afeedback signal from an output of the regulated power supply. Thecontrol module compares the feedback signal to a range, transitions fromthe PWM mode to the transient DCM when the feedback signal is outside ofthe range, transitions from the transient DCM to the steady state DCM,and transitions from the steady state DCM to the PWM mode.

In other features, the regulated power supply includes an energy storagedevice, wherein the control module determines an estimated charging timefor charging the energy storing device to have current through theenergy storage device that is approximately equal to a load currentduring the steady state DCM. The control module charges the energystorage device for the estimated charging time and then transitions fromthe steady state DCM to the PWM mode.

In other features, the regulated power supply includes an analog todigital converter (ADC) that receives the feedback signal and thatgenerates an ADC count. The control module receives the ADC count andswitches between the PWM mode and the transient DCM based on the ADCcount. The control module compares the feedback signal to a range andswitches between the PWM mode and the transient DCM when the feedbacksignal is outside of the range.

In other features, the regulated power supply includes a current sensorthat senses current and generates a current signal and wherein thecontrol module switches between the transient DCM and the steady-stateDCM based on the current signal. An energy storage device is connectedto the inverter. The control module charges the energy storage device byplacing the inverter in an up state until a current through the energystorage device reaches a first predetermined current and wherein theduration of the up state is T_(up). The control module discharges theenergy storage device by placing the inverter in a down state until thecurrent through the energy storage device reaches a second predeterminedcurrent and wherein the duration of the down state is T_(down). Thecontrol module tracks a time T_(off) that is based on an output voltageof the power supply reaching a predetermined voltage and switches fromthe DCM to the PWM mode after a time T_(load) that is based on the timesT_(up), T_(down), and T_(off). A capacitor has one end connected to theenergy storage device. The energy storage device includes an inductor.

A method is provided for operating a regulated power supply. The methodincludes receiving a feedback signal from an output voltage of theregulated power supply, comparing the feedback signal to a range,transitioning from using a pulse width modulation (PWM) mode to generatethe output voltage to using a transient discrete control mode (DCM) togenerate the output voltage when the feedback signal is outside of therange, transitioning from using the transient DCM to using a steadystate DCM to generate the output voltage, and transitioning from usingthe steady state DCM to using the PWM mode to generate the outputvoltage.

In other features, the method includes providing an energy storagedevice and determining an estimated charging time for charging theenergy storing device to have current through the energy storage devicethat is approximately equal to a load current during the steady stateDCM. The method also includes charging the energy storage device for theestimated charging time and then performing said transitioning step fromusing the steady state DCM.

In other features, the method includes generating a count from thefeedback signal. The method also includes receiving the count andtransitioning, based on the count, between using the PWM mode and usingthe transient DCM to generate the output voltage. The method alsoincludes comparing the feedback signal to a range and transitioning,based on the feedback signal being outside of the range, between usingthe PWM mode and using the transient DCM to generate the output voltage.

In other features, the method includes sensing current and generating acurrent signal, and transitioning, based on the current signal, betweenusing the transient DCM and using the steady-state DCM to generate theoutput voltage. The method includes providing an energy storage devicewithin the regulated power supply. The method includes charging theenergy storage device until a current through the energy storage devicereaches a first predetermined current and wherein the duration of thecharging is T_(up), discharging the energy storage device until thecurrent through the energy storage device reaches a second predeterminedcurrent and wherein the duration of the discharging is T_(down),tracking a time T_(off) that is based on the output voltage reaching apredetermined voltage, and transitioning from using the DCM to using thePWM mode after a time T_(oad) that is based on the times T_(up),T_(down), and T_(off). The method includes connecting a capacitor to theenergy storage device. The method includes the energy storage deviceincluding an inductor.

A regulated power supply is provided that includes inverter meanscomprising upper switch means for switching and lower switch means forswitching that are connected in series. The regulated power supply alsoincludes control means for selectively controlling the upper switchmeans and the lower switch means in one of a pulse width modulation(PWM) mode, a transient discrete control mode (DCM), and a steady stateDCM and for receiving a feedback signal from an output of the regulatedpower supply. The control means compares the feedback signal to a range,transitions from the PWM mode to the transient DCM when the feedbacksignal is outside of the range, transitions from the transient DCM tothe steady state DCM, and transitions from the steady state DCM to thePWM mode.

In other features, the regulated power supply includes energy storagemeans, wherein the control means determines an estimated charging timefor charging energy storage means to have current through the energystorage means that is approximately equal to a load current during thesteady state DCM. The control means charges the energy storage means forthe estimated charging time and then transitions from the steady stateDCM to the PWM mode.

In other features, the regulated power supply includes an analog todigital converter (ADC) means for receiving the feedback signal andgenerating an ADC count. The control means receives the ADC count andswitches between the PWM mode and the transient DCM based on the ADCcount. The control means compares the feedback signal to a range andswitches between the PWM mode and the transient DCM when the feedbacksignal is outside of the range.

In other features, the regulated power supply includes a current sensormeans for sensing current and generating a current signal and whereinthe control means switches between the transient DCM and thesteady-state DCM based on the current signal. The regulated power supplyincludes an energy storage means connected to the inverter means. Thecontrol means charges the energy storage means by placing the invertermeans in an up state until a current through the energy storage meansreaches a first predetermined current and wherein the duration of the upstate is T_(up). The control means discharges the energy storage meansby placing the inverter means in a down state until the current throughthe energy storage means reaches a second predetermined current andwherein the duration of the down state is T_(down). The control meanstracks a time T_(off) that is based on an output voltage of the powersupply reaching a predetermined voltage and switches from the DCM to thePWM mode after a time T_(load) that is based on the times T_(up),T_(down), and T_(off). The regulated power supply includes a capacitormeans for providing a capacitance, where the capacitor means includesone end connected to the energy storage device. The energy storage meansincludes an inductor means for providing an inductance.

A control module for a regulated power supply is provided and includesan analog to digital converter (ADC) that generates a digital feedbacksignal from an analog feedback signal. A switch control module generatesa first switch control signal and a second switch control signal. A modeselection module compares the digital feedback signal to a range andchanges the switch control module from a pulse width modulation (PWM)mode to a discrete control mode (DCM) when the digital feedback signalis outside of the range.

In other features, the DCM includes a transient DCM and a steady-stateDCM. The control module includes an input that receives a current signaland the mode selection module changes the switch control module from thetransient DCM to the steady-state DCM based on the current signal andthe digital feedback signal. The mode selection module measures timingrelationships between the current signal and digital feedback signalwhen the switch control module is operating in the steady-state DCM andchanges the switch control module from steady-state DCM to PWM based onthe timing relationships.

A control method for a regulated power supply is provided and includesgenerating a digital feedback signal from an analog feedback signal,generating a first switch control signal and a second switch controlsignal, comparing the digital feedback signal to a range and changingthe first switch control signal and the second switch control signalfrom a pulse width modulation (PWM) compatible mode to a discretecontrol mode (DCM) compatible mode when the digital feedback signal isoutside of the range.

In other features, the DCM compatible mode includes a transient DCMcompatible mode and a steady-state DCM compatible mode. The controlmethod further includes receiving a current signal and changing from thetransient DCM compatible mode to the steady-state DCM compatible modebased on the current signal and the digital feedback signal. The controlmethod further includes measuring timing relationships between thecurrent signal and the digital feedback signal when the first switchcontrol signal and the second switch control signal are operating in thesteady-state DCM compatible mode, and changing from the steady-state DCMcompatible mode to the PWM compatible mode based on the timingrelationships.

A control module for a regulated power supply is provided and includesanalog to digital converter (ADC) means for generating a digitalfeedback signal from an analog feedback signal, switch control means forgenerating a first switch control signal and a second switch controlsignal, and mode selection means for comparing the digital feedbacksignal to a range and changing the switch control means from a pulsewidth modulation (PWM) mode to a discrete control mode (DCM) when thedigital feedback signal is outside of the range.

In other features, the DCM includes a transient DCM and a steady-stateDCM. The control module further includes input means for receiving acurrent signal and the mode selection means changes the switch controlmeans from the transient DCM to the steady-state DCM based on thecurrent signal and the digital feedback signal. The mode selection meansmeasures timing relationships between the current signal and digitalfeedback signal when the switch control means is operating in thesteady-state DCM, and changes the switch control means from steady-stateDCM to PWM based on the timing relationships.

In still other features, the systems and methods described above areimplemented by a computer program executed by one or more processors.The computer program can reside on a computer readable medium such asbut not limited to memory, non-volatile data storage and/or othersuitable tangible storage mediums.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 illustrates a waveform of a regulated output voltage from avoltage regulator of the prior art;

FIG. 2A illustrates a schematic diagram of a voltage regulator;

FIG. 2B illustrates a state chart of switch states of an inverter of thevoltage regulator of FIG. 2A;

FIG. 3 illustrates a functional block diagram of a controller for avoltage regulator;

FIG. 4 illustrates waveforms of a voltage regulator that is operating ina pulse-width modulated (PWM) mode;

FIG. 5 illustrates waveforms of a voltage regulator that is operating ina steady-state discrete control mode (DCM);

FIG. 6A illustrates a state diagram of transitions between operatingmodes of a voltage regulator;

FIG. 6B illustrates steps of a method for operating a voltage regulator;and

FIGS. 7A and 7B illustrate waveforms of a voltage regulator that isswitching between a PWM mode, a transient DCM, and a steady-state DCM;

FIG. 8A illustrates the present invention arranged in a hard disk drive;

FIG. 8B illustrates the present invention arranged in a digitalversatile disc;

FIG. 8C illustrates the present invention arranged in a high definitiontelevision;

FIG. 8D illustrates the present invention arranged in a control systemof a vehicle;

FIG. 8E illustrates the present invention arranged in a cellular phone;

FIG. 8F illustrates the present invention arranged in a set top box; and

FIG. 8G illustrates the present invention arranged in a media player.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. For purposes of clarity, the same referencenumbers will be used in the drawings to identify similar elements. Asused herein, the term module, circuit and/or device refers to anApplication Specific Integrated Circuit (ASIC), an electronic circuit, aprocessor (shared, dedicated, or group) and memory that execute one ormore software or firmware programs, a combinational logic circuit,and/or other suitable components that provide the describedfunctionality. As used herein, the phrase at least one of A, B, and Cshould be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present invention.

Referring now to FIG. 2A, a schematic diagram of a voltage regulator 50is shown. The voltage regulator 50 includes an inverter 51 thatcomprises an upper switch 51 and a lower switch S2. The upper and lowerswitches S1, S2 are connected in series between an unregulated powersupply V_(in) and a reference node 52, such as ground or other referencepotential. The upper switch 51 and the lower switch S2 can be providedby transistors, triacs, thyristors, and/or any other suitable switchingdevices.

A node 54 is located between the upper switch 51 and the lower switch S2and is connected to one end of an inductor L. A current sensor 55measures an inductor current I_(L) and generates an inductor currentsignal to a control module 56. A second end of the inductor L isconnected to a first end of a capacitor C and an output terminal 58. Asecond end of the capacitor C is connected to the reference node 52. Aresistor R represents a load that is connected across a regulated outputvoltage V_(out) (across the output terminal 58 and the reference node52). The load passes a load current I_(load).

A feedback signal 60 feeds back the regulated output voltage V_(out) toan input of the control module 56. The feedback signal 60 may bemodified by an optional compensation network module 62. The compensationnetwork 62 can include various proportional, integral, derivative, lead,and/or lag function modules connected in various combinations. Theparticular combination used in an application dependes on a desiredsettling time and/or degree of regulation that is desired of theregulated output voltage V_(out). The control module 56 includes an ADC64 that converts the feedback signal 60 to a digital count. The controlmodule 56 may be powered by the unregulated power supply V_(in). Thecontrol module 56 also includes a timer module 65 for tracking timesT_(up), T_(down), T_(off), and T_(load) as described below.

The voltage regulator 50 can operate in a plurality of different modes.The voltage regulator 50 generally operates in a PWM mode until thefeedback signal 60 voltage, V_(fb), causes the ADC 64 to go out ofrange. The ADC goes out of range when the feedback signal voltage,V_(fb), exceeds a voltage range that correlates with the ADC's 64 rangeof digital counts. For example, the ADC 64 may be out of range when thevoltage regulator 50 is first switched on or when the load currentI_(load) changes abruptly. When the ADC 64 goes out of range, it can bedifficult for the PWM mode to remain stable and/or keep the regulatedoutput voltage V_(out) within a desired range or tolerance. The voltageregulator 50 therefore switches through a transient discrete controlmode (DCM) and a steady-state DCM upon the ADC 64 going out of range.The DCMs are inherently stable and the voltage regulator 50 remains inthe DCMs while it estimates a charging time for the inductor L to havethe load current I_(load). The voltage regulator 50 uses the chargingtime to charge the inductor L and then re-enters the PWM mode in astable condition.

This multi-mode method allows the voltage regulator 50 to operate with alow-power and low-resolution ADC 64 without requiring complex controlalgorithms and/or complex functions in the compensation network module62. The following description details how the voltage regulator 50operates in the PWM mode, the transient DCM, and the steady-state DCM.The description then provides working examples of the voltage regulator50 switching between the PWM mode, the transient DCM, and thesteady-state DCM.

Referring now to FIG. 2B, a state chart 70 indicates whether the upperswitch S1 and the lower switch S2 are open or closed for differentoperating states of the inverter 51. In an up state 72, the upper switchS1 is closed and the lower switch S2 is open. In a down state 74, theupper switch S1 is open and the lower switch S2 is closed. In an offstate 76, the upper switch S1 is open and the lower switch S2 is open.

Referring now to FIG. 3, a functional block diagram is shown of thecontrol module 56. A mode select module 66 determines in which one ofthe plurality of different modes to operate the voltage regulator 50.The mode select module 66 makes the determination based on inputs fromthe ADC 64 and a comparator module 67. The comparator module 67 receivesthe inductor current signal from the current sensor 55 and compares theinductor current signal to one or more predetermined current levels. Thecomparator module 67 then communicates a comparison result to the modeselect module 66.

The mode select module 66 includes an output that communicates with aswitch control circuit 68. The switch control circuit 68 generates afirst switch control signal 69-1 and a second switch control signal 69-2that control the first and second switches S1 and S2, respectively. Thefirst switch control signal 69-1 and the second switch control signal69-2 are referred to collectively as the switch control signals 69. Theswitch control circuit 68 generates the switch control signals 69 suchthat they open and close the first and second switches S1, S2 accordingto the operating mode selected by the mode select module 67. A detaileddescription of the operation of the first and second switches S1, S2, ascontrolled by the switch control signals 69, is provided in thefollowing description.

Referring now to FIG. 4, an unscaled waveform of inductor current I_(L)is shown while the voltage regulator 50 is operating in the PWM mode.The inductor current I_(L) is shown with respect to I_(L)=0. The PWMmode provides less inductor current I_(L) ripple than the transient DCMand the steady-state DCM; however the PWM mode can require a complexcontrol algorithm to maintain stability if the ADC 64 drops out ofrange. Therefore, the voltage regulator 50 only operates in the PWM modeuntil the ADC 64 drops out of range, and then temporarily switches tothe DCMs in accordance with a method described below.

Operation of the PWM mode will now be described. A PWM cycle begins at atime 78. At the time 78, the control module 56 places the inverter 51 inthe up state 72 for a time T_(up). At the end of the time T_(up), thecontrol module 56 places the inverter 51 in the down state for a timeT_(down), thereby ending the PWM cycle.

The sum of the times T_(up) and T_(down) is a constant period, T. Insome embodiments the period T is equal to one microsecond, whichcorresponds to a frequency of one megahertz. The durations of the timesT_(up) and T_(down) are a function of the comparison between the averagefeedback signal 60 voltage V_(fb) and a set point voltage V* of thecontrol module 56. The control module 56 increases the time T_(up) anddecreases the time T_(down) when the comparison indicates that theaverage feedback signal 60 voltage V_(fb) is less than the set pointvoltage V. The control module 56 decreases the time T_(up) and increasesthe time T_(down) when the comparison indicates that the averagefeedback signal 60 voltage V_(fb) is greater than the set point voltageV*.

A ratio of T_(up) and T_(down) is referred to as a duty cycle D, whichcan be mathematically represented asD=T _(up) /T, substituting for T gives  (1)D=T _(up)/(T _(down) +T _(up)).  (2)Also,D=V _(out) /V _(in).  (3)

Referring now to FIG. 5, unscaled waveforms of the inductor currentI_(L) and the regulated output voltage V_(out) are shown while thevoltage regulator 50 is operating in the steady-state DCM. The voltageregulator 50 operates in the steady-state DCM after the ADC 64 has goneout of range and completed the transient DCM, which is described below.The steady-state DCM allows the control module 56 to estimate thecharging time for the inductor L to have an averaged inductor currentĪ_(L) approximately equal to the load current I_(load) and then switchesback to the PWM mode with the ADC 64 back in range.

A steady-state DCM cycle begins at a time 80. At the time 80, thecontrol module 56 places the inverter 51 in the up state 72 until theinductor current I_(L) rises to a peak current I_(DCM), which occurs ata time 82. The value of I_(DCM) is fixed and is generally chosen to beabout 100% greater than a maximum expected load current I_(load). Thecontrol module 56 records the time T_(up) as the difference between thetime 82 and the time 80. The duration of the time T_(up) is notnecessarily the same between the DCM and PWM modes.

When the inductor current I_(L) reaches I_(DCM), the control module 56places the inverter 51 in the down state 74 until the inductor currentI_(L) falls to zero, which occurs at a time 84. The control module 56records the time T_(down) as the difference between the time 84 and thetime 82. The duration of the time T_(down) is not necessarily the samebetween the DCM and PWM modes.

After the time 84, the control module 56 places the inverter 51 in theoff state 76, which turns off the inductor current I_(L). The controlmodule 56 holds the inverter 51 in the off state 76 until the feedbacksignal 60 indicates that the regulated output voltage V_(out) hasreached a lower threshold V*−δ, where δ is a maximum output swing of theADC 64. The control module 56 records the duration of the off state 76as a time T_(off). This completes the steady-state DCM cycle.

During the steady-state DCM cycle, the charge dissipated through theload during the time T_(off) is equal to the charge accumulated in thecapacitor C during the times T_(up) and T_(down). This relationship isshown mathematically asI _(load)=0.5*(T _(up) +T _(down))*I _(DCM)/(T _(up) +T _(down) +T_(off)) where  (4)I _(DCM)=(T _(down) *V _(out) /L).  (5)

The control module 56 uses this relationship in the method describedbelow. The method sets the inductor current I_(L) equal to the loadcurrent I_(load) prior to returning the voltage regulator 50 to the PWMmode.

Referring now to FIG. 6A, a method 100 is shown for switching thevoltage regulator 50 between the PWM mode, the transient DCM, and thesteady-state DCM. The method 100 allows the voltage regulator 50 tonormally operate in the PWM mode and have a low ripple current throughthe inductor L. However, if the ADC 64 goes out of range, the method 100causes the voltage regulator 50 to briefly operate in the inherentlystable DCMs. Since the DCMs have a higher ripple current through theinductor than the PWM mode, the voltage regulator 50 operates in theDCMs only until it can be switched back to the PWM mode with the ADC 64back in range.

The method 100 can be stored as a computer program in a memory (notshown) of the mode select module 66. The mode select module 66 caninclude a microprocessor (not shown) that is connected to the memory andexecutes the method 100.

Control begins in the PWM state 102, which places the voltage regulator50 in the PWM mode. Control changes to a transient DCM state 104 whenthe ADC 64 goes out of range. In the transient DCM state 104, thevoltage regulator 50 operates in the transient DCM, which is detailedbelow, until the comparator module 66 determines that the inductorcurrent I_(L) is equal to zero and the ADC 64 indicates that theregulated output voltage V_(out) is equal to V*−δ.

After the transient DCM state 104, control changes to a steady-state DCMstate 106. In the steady-state DCM state 106, the mode select module 66operates the voltage regulator 50 in the steady-state DCM, which wasdescribed above, to determine the time T_(load). The time T_(load)represents how long the inverter 51 must operate in the up state 72 ofthe steady-state DCM cycle to make the inductor current I_(L) equal tothe load current I_(load). During the steady-state DCM cycle, the timeT_(load) is provided by the equationT _(load)=[0.5*(T _(up) ++T _(dowm))*T _(up) ]/[T _(up) +T _(down) +T_(off)].  (6)Control remains in the steady-state DCM state 106 until it determinesT_(load) in accordance with equation (6) and holds the inverter 51 inthe up state 72 for the duration of T_(load). Once the time T_(load) hasexpired, the inductor current I_(L) and the load current I_(load) areapproximately equal and control switches back to the PWM state 102 withthe ADC 64 back in range.

Referring now to FIG. 6B, a flow chart representation of the method 100is shown. Control enters at block 110 and proceeds to decision block112. In decision block 112, control determines whether the voltageregulator 50 is presently operating in DCM. If not, control proceeds todecision block 114 and determines whether the ADC 64 is out of range. Ifnot, control proceeds to block 116 and operates the voltage regulator 50in the PWM mode (FIG. 3). On the other hand, if the ADC 64 is out ofrange in decision block 114, then control proceeds to block 120 andoperates the voltage regulator 50 in the DCM. Control exits throughblock 118 after it completing one of block 116 and 120.

Returning now to decision block 112, control proceeds to decision block122 when the voltage regulator 50 is operating in DCM. In decision block122 control determines whether the voltage regulator 50 has completedone cycle of steady-state DCM (FIG. 4) since control last entered DCM atblock 120. If one cycle of steady-state DCM has not been completed, thencontrol proceeds to block 120 and continues operating the voltageregulator 50 in DCM. On the other hand, if one cycle of steady-state DCMhas been completed in decision block 122, then control proceeds to block124 and determines T_(load) as described above. Control then proceeds toblock 126 and places the inverter 51 in the up state 72. Control thenproceeds to block 128 and holds the inverter 51 in the up state 51 forthe time T_(load). Control then proceeds to block 116 and returns tooperating the voltage regulator 50 in the PWM mode. Referring now toFIG. 7A, operation of the voltage regulator 50 will be described. Theworking example of FIG. 7A assumes that the optional compensationnetwork module 62 is not used so that V_(fb)=V_(out). If a compensationnetwork module is employed, appropriate correction may be performed.

The voltage regulator 50 operates in the PWM state 102 so long as theregulated output voltage V_(ow) remains within the range of the ADC 64.At a time 150, the load current I_(load) abruptly increases and causesthe regulated output voltage V_(out) to drop below V*−δ. The drop in theregulated output voltage V_(out) causes the ADC 64 to go out of range ata time 151. Control therefore switches the voltage regulator 50 to thetransient DCM state 104.

Upon entering the transient DCM state 104, the control module 56switches the inverter 51 to the up state 72 until the regulated outputvoltage V_(out) is equal to V*, which occurs at a time 152. After thetime 152, the control module 56 switches the inverter 51 to the downstate 74 until the inductor current I_(L) is equal to zero, which occursat a time 154. At the time 154, the control module 56 switches theinverter 51 to the off state 76 until the regulated output voltageV_(out) falls to V*−δ, which occurs at a time 156.

The time 156 marks the end of the transient DCM state 104 and thebeginning of the steady-state DCM state 106. At the time 156, thecontrol module 56 begins the process of using T_(up), T_(down), andT_(off) to determine T_(load). At the time 156, the control module 56switches the inverter 51 to the up state 72 until the inductor currentI_(L) is equal to I_(DCm), which occurs at a time 158. The time T_(up)is equal to the difference between the times 158 and 156. After theinductor current I_(L) reaches I_(DCM), the control module 56 switchesthe inverter 51 to the down state 74 until the inductor current I_(L) isequal to zero, which occurs at a time 160. The time T_(down) is equal tothe difference between the times 160 and 158.

At the time 160, the control module 56 switches the inverter 51 to theoff state 76. The control module 56 keeps the inverter 51 in the offstate 76 until the regulated output voltage V_(out) falls to V*−δ, whichoccurs at a time 162. The time T_(off) is equal to the differencebetween the times 160 and 162.

At the time 162, the control module 56 determines T_(load) in accordancewith equation (6) and the times T_(up), T_(down), and T_(off). Thecontrol module 56 then switches the inverter 51 to the up state 72 forthe time T_(load). The time T_(load) expires at a time 164. At the time164, the inductor current I_(L) is equal to the load current I_(load),within approximation errors of the control module 56, and controlswitches back to the PWM state 102. When control switches back to thePWM state 102, the regulated output voltage V_(out) will be between V*−δand V*+δ and the control module 56 is able to resume stable operation inthe PWM mode.

Referring now to FIG. 7B, the method 100 is shown being used when theregulated output voltage V_(out) rises out of range due to an abruptdecrease in the load current I_(load) at the time 150. The decreasedload current I_(load) causes the regulated output voltage V_(out) torise out of range at the time 152. Since the regulated output voltage isalready above V*, the transient DCM state 104 skips placing the inverter51 in the up state 72. Instead, the transient DCM state 104 begins byplacing the inverter 51 in the down state 74 at the time 152. Controlthen switches the inverter 51 to the off state 76 when the inductorcurrent I_(load) falls to zero at the time 154. At the time 154, controlswitches the inverter 51 to the off state 76 until the regulated outputvoltage V_(out) falls to V*−δ, which occurs at the time 156. From thetime 156 onward, control enters the steady-state DCM state 106,determines T_(lOad), and returns to the PWM state 102 as describedabove.

Referring now to FIGS. 8A-8G, various exemplary implementations of thepresent invention are shown. Referring now to FIG. 8A, the presentinvention can be implemented in a hard disk drive 400. The presentinvention may implement at least a portion of a regulated power supplymodule 407. The power supply module 407 includes one or more outputsthat provide power to one or more of elements of the HDD 400. In someimplementations, a signal processing and/or control circuit 402 and/orother circuits (not shown) in the HDD 400 may process data, performcoding and/or encryption, perform calculations, and/or format data thatis output to and/or received from a magnetic storage medium 406.

The HDD 400 may communicate with a host device (not shown) such as acomputer, mobile computing devices such as personal digital assistants,cellular phones, media or MP3 players and the like, and/or other devicesvia one or more wired or wireless communication links 408. The HDD 400may be connected to memory 409 such as random access memory (RAM), lowlatency nonvolatile memory such as flash memory, read only memory (ROM)and/or other suitable electronic data storage.

Referring now to FIG. 8B, the present invention can be implemented in adigital versatile disc (DVD) drive 410. The present invention mayimplement at least a portion of a regulated power supply module 415. Thepower supply module 415 includes one or more outputs that provide powerto one or more elements of the DVD drive 410. A signal processing and/orcontrol circuit 412 and/or other circuits (not shown) in the DVD drive410 may process data, perform coding and/or encryption, performcalculations, and/or format data that is read from and/or data writtento an optical storage medium 416. In some implementations, the signalprocessing and/or control circuit 412 and/or other circuits (not shown)in the DVD drive 410 can also perform other functions such as encodingand/or decoding and/or any other signal processing functions associatedwith a DVD drive.

The DVD drive 410 may communicate with an output device (not shown) suchas a computer, television or other device via one or more wired orwireless communication links 417. The DVD drive 410 may communicate withmass data storage 418 that stores data in a nonvolatile manner. The massdata storage 418 may include a hard disk drive (HDD). The HDD may havethe configuration shown in FIG. 8A. The HDD may be a mini HDD thatincludes one or more platters having a diameter that is smaller thanapproximately 1.8″. The DVD drive 410 may be connected to memory 419such as RAM, ROM, low latency nonvolatile memory such as flash memoryand/or other suitable electronic data storage.

Referring now to FIG. 8C, the present invention can be implemented in ahigh definition television (HDTV) 420. The present invention mayimplement at least a portion of a regulated power supply module 421. Thepower supply module 421 includes one or more outputs that provide powerto one or more elements of the HDTV 420.

The HDTV 420 receives HDTV input signals in either a wired or wirelessformat and generates HDTV output signals for a display 426. In someimplementations, a signal processing circuit and/or control circuit 422and/or other circuits (not shown) of the HDTV 420 may process data,perform coding and/or encryption, perform calculations, format dataand/or perform any other type of HDTV processing that may be required.

The HDTV 420 may communicate with mass data storage 427 that stores datain a nonvolatile manner such as optical and/or magnetic storage devices.At least one HDD may have the configuration shown in FIG. 8A and/or atleast one DVD may have the configuration shown in FIG. 8B. The HDD maybe a mini HDD that includes one or more platters having a diameter thatis smaller than approximately 1.8″. The HDTV 420 may be connected tomemory 428 such as RAM, ROM, low latency nonvolatile memory such asflash memory and/or other suitable electronic data storage. The HDTV 420also may support connections with a WLAN via a WLAN network interface429.

Referring now to FIG. 8D, the present invention can be implemented in acontrol system of a vehicle 430, a WLAN interface and/or mass datastorage of a vehicle control system. The present invention may implementat least a portion of a regulated power supply module 449. The powersupply module 449 includes one or more outputs that provide power to oneor more elements of the vehicle 430. In some implementations, thepresent invention can be implemented in a powertrain control system 432that receives inputs from one or more sensors such as temperaturesensors, pressure sensors, rotational sensors, airflow sensors and/orany other suitable sensors and/or that generates one or more outputcontrol signals such as engine operating parameters, transmissionoperating parameters, and/or other control signals.

The present invention may also be implemented in other control systems440 of the vehicle 430. The control system 440 may likewise receivesignals from input sensors 442 and/or output control signals to one ormore output devices 444. In some implementations, the control system 440may be part of an anti-lock braking system (ABS), a navigation system, atelematics system, a vehicle telematics system, a lane departure system,an adaptive cruise control system, a vehicle entertainment system suchas a stereo, DVD, compact disc and the like. Still other implementationsare contemplated.

The powertrain control system 432 may communicate with mass data storage446 that stores data in a nonvolatile manner. The mass data storage 446may include optical and/or magnetic storage devices for example harddisk drives HDD and/or DVDs. At least one HDD may have the configurationshown in FIG. 8A and/or at least one DVD may have the configurationshown in FIG. 8B. The HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″. Thepowertrain control system 432 may be connected to memory 447 such asRAM, ROM, low latency nonvolatile memory such as flash memory and/orother suitable electronic data storage. The powertrain control system432 also may support connections with a WLAN via a WLAN networkinterface 448. The control system 440 may also include mass datastorage, memory and/or a WLAN interface (all not shown).

Referring now to FIG. 8E, the present invention can be implemented in acellular phone 450 that may include a cellular antenna 451. The presentinvention may implement at least a portion of a regulated power supplymodule 470. The power supply module 470 includes one or more outputsthat provide power to one or more elements of the cellular phone 450.

In some implementations, the cellular phone 450 includes a microphone456, an audio output 458 such as a speaker and/or audio output jack, adisplay 460 and/or an input device 462 such as a keypad, pointingdevice, voice actuation and/or other input device. The signal processingand/or control circuits 452 and/or other circuits (not shown) in thecellular phone 450 may process data, perform coding and/or encryption,perform calculations, format data and/or perform other cellular phonefunctions.

The cellular phone 450 may communicate with mass data storage 464 thatstores data in a nonvolatile manner such as optical and/or magneticstorage devices for example hard disk drives HDD and/or DVDs. At leastone HDD may have the configuration shown in FIG. 8A and/or at least oneDVD may have the configuration shown in FIG. 8B. The HDD may be a miniHDD that includes one or more platters having a diameter that is smallerthan approximately 1.8″. The cellular phone 450 may be connected tomemory 466 such as RAM, ROM, low latency nonvolatile memory such asflash memory and/or other suitable electronic data storage. The cellularphone 450 also may support connections with a WLAN via a WLAN networkinterface 468.

Referring now to FIG. 8F, the present invention can be implemented in aset top box 480. The present invention may implement at least a portionof a regulated power supply module 497. The power supply module 497includes one or more outputs that provide power to one or more elementsof the set top box 480.

The set top box 480 receives signals from a source such as a broadbandsource and outputs standard and/or high definition audio/video signalssuitable for a display 488 such as a television and/or monitor and/orother video and/or audio output devices. The signal processing and/orcontrol circuits 484 and/or other circuits (not shown) of the set topbox 480 may process data, perform coding and/or encryption, performcalculations, format data and/or perform any other set top box function.

The set top box 480 may communicate with mass data storage 490 thatstores data in a nonvolatile manner. The mass data storage 490 mayinclude optical and/or magnetic storage devices for example hard diskdrives HDD and/or DVDs. At least one HDD may have the configurationshown in FIG. 8A and/or at least one DVD may have the configurationshown in FIG. 8B. The HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″. Theset top box 480 may be connected to memory 494 such as RAM, ROM, lowlatency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. The set top box 480 also may supportconnections with a WLAN via a WLAN network interface 496.

Referring now to FIG. 8G, the present invention can be implemented in amedia player 500. The present invention may implement at least a portionof a regulated power supply module 518. The power supply module 518includes one or more outputs that provide power to one or more elementsof the media player 500.

In some implementations, the media player 500 includes a display 507and/or a user input 508 such as a keypad, touchpad and the like. In someimplementations, the media player 500 may employ a graphical userinterface (GUI) that typically employs menus, drop down menus, iconsand/or a point-and-click interface via the display 507 and/or user input508. The media player 500 further includes an audio output 509 such as aspeaker and/or audio output jack. Signal processing and/or controlcircuits 504 and/or other circuits (not shown) of the media player 500may process data, perform coding and/or encryption, performcalculations, format data and/or perform any other media playerfunction.

The media player 500 may communicate with mass data storage 510 thatstores data such as compressed audio and/or video content in anonvolatile manner. In some implementations, the compressed audio filesinclude files that are compliant with MP3 format or other suitablecompressed audio and/or video formats. The mass data storage may includeoptical and/or magnetic storage devices for example hard disk drives HDDand/or DVDs. At least one HDD may have the configuration shown in FIG.8A and/or at least one DVD may have the configuration shown in FIG. 8B.The HDD may be a mini HDD that includes one or more platters having adiameter that is smaller than approximately 1.8″. The media player 500may be connected to memory 514 such as RAM, ROM, low latency nonvolatilememory such as flash memory and/or other suitable electronic datastorage. The media player 500 also may support connections with a WLANvia a WLAN network interface 516. Still other implementations inaddition to those described above are contemplated.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

1. A regulated power supply, comprising: an inverter comprising an upper switch and a lower switch that are connected in series; and a control module that selectively controls the upper switch and the lower switch in one of a pulse width modulation (PWM) mode and a discrete control mode (DCM), that receives a feedback signal from an output of the regulated power supply and that switches between the PWM mode and the DCM based on the feedback signal.
 2. The regulated power supply of claim 1, wherein the control module is configured to: compare the feedback signal to a range of an analog-to-digital converter; and switch between the PWM mode and the DCM when the feedback signal is outside of the range.
 3. The regulated power supply of claim 1, further comprising a current sensor configured to (i) sense current and (ii) generate a current signal, wherein: the control module is configured to, based on the current signal, switch between a transient DCM and a steady-state DCM.
 4. The regulated power supply of claim 1, further comprising an energy storage device, wherein the control module is configured to: charge the energy storage device by placing the inverter in an up state until a current through the energy storage device is equal to a first predetermined current level, wherein a duration of the up state is a first period; discharge the energy storage device by placing the inverter in a down state until the current through the energy storage device is equal to a second predetermined current level, wherein a duration of the down state is a second period; open the upper switch and the lower switch for a third period based on an output voltage of the regulated power supply being equal to a predetermined voltage; and switch from the DCM to the PWM mode subsequent to a fourth period, and determine the fourth period based on the first period, the second period and the third period. 